Refractory lining for melting pots



Patented Aug. 2, 1932 EJNITED- STATES GERALD R. BROPHY, OF SCHENEGTAIDY, NEW.YDBK, AND GUISEPPE SGORZONI, OF EAST LYNN, MASSACHUSETTS, ASSIGNOBS TO GENERAL ELECTRIC COMPANY, A CORPORA- TION OF NEW YORK REFRACTORY LINING FOR MELTING POTS No Drawing.

The present invention relates to refractory materials and more particularly to linings for metal receptacles or pots which are adapted to contain molten metals. In the use of such receptacles considerable difliculty has heretofore been encountered owing to the tendency of the moltenmetal to dissolve the metal of the receptacle. For example, when molten aluminum is placed in iron or steel containers, it is not unusual for the aluminum to dissolve the metal of the container to such an extent that the amount of ferrous metal contained in the aluminum may be 4 or 5 per cent of the aluminum content. The presence of this dissolved metal in the aluminum is undesirable since it renders the aluminum brittle and adversely affects its conductivity. In the case of die-casting alloys, the dissolved metal renders the alloys sluggish and difiicult to handle.

In order to protect metal containers from the action of molten metal, various expedients have from time to time been suggested, among which may be mentioned the application of a lime wash, such as common whitewash, to the inside of the metal container. While such a wash is more or less efiective in preventing the dissolving action of the molten metal and in preserving the metal container, it is undesirable since it must frequently be renewed.

According to the present invention a refractory lining has been prepared which may be fused to the inner surface of the metal container providing thereby a permanent coating for the metal container which is adapted to protect the metal of the container and to prevent contamination of the molten metal by metal dissolved from the container.

In carrying the invention into effect calcium hydroxide, in the form of slaked white lime slag from steel melting furnaces, is mixed with either magnesium sulphate or borax, and ground white enamel, such as used for coating cast iron. These constituents are ground together very thoroughly and then made into a thin paste or wash with water to which a small amount of sticky organic binder material, such as molasses, has been added. The metal container to be coated is Serial No. 178,806.

then heated slightly and the mixture painted on the inside of the container. The coating is allowed to dry and is then placed in a furnace and heated to a temperature high enough to fuse the coating to the metal con- 1 tainer. This temperature may vary from about 500 C. to about 700 C. and is maintained for different periods of time depending on the thickness of'the metal container. For a container about of an inch thick a period of about two hours will be found sufficient to bring all portions of thecontainer to the desired temperature. Owing to the fact that cast iron contains a relatively large amount of occluded gas, a firing temperature of 700 0. should not be exceeded when the container is made of this metal since above this point occluded gas will be given ofi and the coating will blister. A temperature greater than 700 C. may be exceeded, however, if the container is made of steel. After the coating has been applied to the container and fired in the manner indicated, it is immaterial what temperatures are thereafter employed in the use of the container.

If desired a second coat may be applied to the container and fused in the same manner as the first coat. Any pin holes which may remain after the application of the second coat may be closed by merely applying a thick paste of the coating material to the pin holes. The coating of the above material when applied as indicated fuscs to the inner surface of the container, the coating and metal of the container being mutually soluble to a certain extent in one another.

The proportions of material employed in the refractory lining are approximately as follows:

100 parts by weight of calcium hydroxide 6 parts by weight of magnesium sulphate or borax I 25 parts by weight of enamel 12 parts by weight of molasses All the figures given may be subject to variations within limits both above and below the figures given, although it will in general be found that the most satisfactory results will be obtained with the above proportions.

The enamel employed is a vitreous enamel of the hero-silicate type, such as commonly employed in coating cast iron. Although its presence in the composition is desirable, owing to its tendency to harden the product and to make it more stonelike, a satisfactory product may be obtained when the enamel is omitted.

The magnesium sulphate, or borax is employed in the heat resistant composition as a binder member and acts to cement the particles of the composition together. At the firing temperature employed the binder member will fuse the mixture to the walls of the container. W hile a binder consisting of either magnesium sulphate or borax gives very satisfactory results, it is possible to use other binders. Sodium silicate, for example, may be employed as a binder when the refactory lining is to be employed with containers for molten lead or tin, although this binder will not prove satisfactory in containers holding molten aluminum. The molasses water employed acts as a temporary binder to hold the particles of the composition together and to hold the mixture on to the container wall while it is being fired.

While the refractory lining described is particularly efficient in protecting ferrous metal containers from the action of molten aluminum or aluminum alloys, its use is not limited to ferrous metal containers adapted to hold aluminum or its alloys. Containers made of alloy metals, such as nickle chrome f alloys, may be lined with the above refractory material if desired and may be employed to hold metals such as molten lead with satisfactory results.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. The method of coating a metal recep tacle which comprises applying to the inner surface of said receptacle a mixture consisting largely of calcium hydroxide but containing water, an organic binder and an in.- organic binder, drying said coating and then baking said coating at a temperature varying from about 500 C. to about 700 C.

2. A refractory coating material consisting of about parts calcium hydroxide,

about 6 parts of an inorganic binder material, about 26 parts vitreous enamel and about 12 parts of an organic binder.

In witness whereof, we have hereunto respectively set our hands the 21st day of March, 1927 and the 23rd day of March,

GERALD R. BROPHY. GUISEPPE SCORZONI. 

